On Friday, LeBron James of the Miami Heat tweeted a photo of the basketball team, wearing hoodies and with heads bowed, alongside the hashtag “WeWantJustice.”

The same day, Fox News commentator Geraldo Rivera ignited widespread criticism for saying on the “Fox & Friends” morning show that “The hoodie is as much responsible for Trayvon Martin’s death as George Zimmerman was.” He continued his assault on “The O’Reilly Factor,” warning parents of black and Hispanic youths not to allow their sons to wear hooded sweatshirts.

“Who else wears hoodies?” he asked. “Everybody that ever stuck up a convenience store; D.B. Cooper, the guy that hijacked a plane; Ted Kaczynski the Unabomber.”

And Daniel Maree, 24, who spearheaded Wednesday’s“Million Hoodie March” in New York — which was followed by rallies in Los Angeles, Atlanta, Detroit and Washington — said he wanted to draw attention not just to Martin’s death, but to the hoodie and all it represents.

“I’ve had experiences where I’ve been walking down the street in New York, and as an African American man in a hoodie, I can tell you it’s seen as in­cred­ibly suspicious,” said Maree, a digital strategist in New York. “Some people hold their purses a little tighter. When I heard Trayvon was wearing a hoodie, I thought, ‘I’ve felt this before.’ ”

So how did this ubiquitous garment — worn by college students and soccer moms, skateboarders and kids on the street — come to be associated with sinister activity?

“Most pieces of material culture have symbolic qualities associated with them,” said Darnell Hunt, professor of sociology and director of the Ralph J. Bunche Center for African American Studies at UCLA. “The hoodie is a pretty generic piece of clothing, but because of the contexts and the groups it’s associated with, it took on different meanings. Just like sagging pants, it was a macho, street-swagger symbol of hip-hop culture, even though it originated in medieval Europe.”

A history of the hoodie

Hoods were worn by monks and scholars in the Middle Ages. The Metropolitan Museum of Art in New York has a child’s hooded tunic that dates back to the seventh century. Dante Alighieri, the 14th-century Florentine poet who wrote “The Divine Comedy,” is rarely depicted without his hood. In some climates, the hood was used to contain body heat, while in Northern Africa’s Maghreb region, the unisex djellaba, a long robe with a pointed hood, is still worn to protect the wearer from the sand and sun. And it could always be used to conceal the identity of the wearer.

The hooded sweatshirt was commercialized in the 1930s by Champion, the American sportswear company, to protect workingmen from the elements. And Daniel James Cole, professor of fashion history at the Fashion Institute of Technology, says that later in that decade, American high fashion adopted the hood: “The American designer Claire McCardell popularized it for women in the early 1940s. One really popular coat style was an A-line swing coat with the hood on it, and there were hooded playsuits and even hooded wedding dresses.”

It wasn’t until the mid-1970s, when Rocky Balboa wore a hooded sweatshirt while running up the steps of the Philadelphia Museum of Art in “Rocky,”that the hooded sweatshirt with its convenient front pocket became a hallmark of unisex sportswear. In the 1990s, hip-hop artists and street culture adopted it as the street-wear uniform of choice — and the term “hoodie” became commonplace, according to Merriam Webster, in 1992.

“Hip-hop culture took it from general vernacular clothing and certainly increased . . . its popularity,” Cole said. “It became cool, and fashion adopted it soon after. You have sleeveless hoodies, which takes away the idea of wearing a hood for warmth. It’s become vernacular.”

Since designers such as Tommy Hilfiger popularized them in the mid-1990s, hoodies sell at all price points, at both Neiman Marcus and Wal-Mart. A hooded jacket by Altuzarra will cost you $2,495. They know no class or cultural borders. Some schools, including several in D.C., have banned the garment for its sloppiness or because it’s a convenient way to hide contraband items or test answers. They’re worn by gangsters, rappers, surfers, skaters and athletes; indie rock fans wear hoodies almost as often as they wear Chuck Taylors; and hoodies have been preppified by brands such as Hollister, a popular teen label Martin wore in a photo released by his parents.

In parts of New Zealand and Australia, there are “Hoodie Free Zones” enforced by store owners and malls to thwart shoplifters. They became a political symbol in the summer during the United Kingdom riots, and in 2006, Prime Minister David Cameron gave a speech claiming, “For young people, hoodies are often more defensive than offensive.” The speech has since been dubbed Cameron’s “hug-a-hoodie” speech.

Cozy and casual, hoodies are called “bunny hugs” in parts of Canada.

Its changing meaning

Still the garment’s meaning remains mixed. Even the word “hoodie” has echoes of racial overtones, differentiated only by prepositions and suffixes. In the hood. From the hood. Hoodlum, derived from “hudelum,” found in a 19th-century German dialect, meaning ruffian.

By concealing the wearer’s identity, a hood can seem sinister: Hooded white men killed black men long before Martin died.

“I think that’s one of the reasons it acquired a sinister connotation,” Hunt said. “It has inherent qualities of mystery and anxiety. You put a hood on and you’re anonymous. The KKK, for example, wore hoods for all those reasons.”

But the shift from Rocky’s triumph to what some see as a threat was recent. Hunt believes that films such as “Menace II Society” and “South Central,” which followed the 1992 Los Angeles riots, propagated the image of the hoodie as a symbol of urban rebellion.

“Things preexist the meanings they acquire,” Hunt said. “Black people have endured the perception that people have about criminality. There’s certain beliefs that some people have about young black men that often lead them to fear them, unjustified. It stands to reason that the hoodie as a style and symbol changed when young black men chose to wear it . . . White youths and older folks in hoodies have relatively benign meanings.”

Denis Wilson noticed the hoodie’s symbolic evolution in 2006. The Philadelphia-based journalist wrote a piece on the hoodie for the New York Times after a friend asked him, “Are you trying to be a gangster?” when he went to a nightclub wearing one.

“Because I’m white, I thought the hoodie was skater,” Wilson said. “But I went back through the history, and I saw the shift when graffiti artists used it to shroud themselves when tagging trains. There’s a connection to the more violent overtones of hip-hop. To ignore the violence in NWA and 50 Cent is silly, but it’s absolutely stupid to think of the hoodie as dangerous. There are hoodies made for nursing mothers.”

In light of Martin’s death, Maree hopes the hoodie — whoever is wearing it — will become a symbol of progress, reminding us of the power of perception and the symbolism we assign to everyday objects.

“I’ll never think of a hoodie the same way I used to,” Maree said. “While I didn’t think about this on the outset, it’s become a way to confront our initial or subliminal reactions to race. It’s subconscious, but when people start to confront their initial reactions, we’ll see progress.”